Scientists have discovered the most distant galaxy ever confirmed, whose light took more than 13 billion years to reach earth, providing a snapshot of the early universe.

One curious trait about the record-breaker is that it forms stars at an incredible rate, about 330 a year - more than a hundred times faster than our Milky Way galaxy. This could be a trademark of the universe's early days, when hydrogen gas for star formation was much more plentiful.

"We wanted to figure out how galaxies evolve," said Steven Finkelstein, lead author and University of Texas astronomer. "One way to do that is to push back deeper and deeper into the history of the universe."

The study was published online in the journal Nature.

At first, the landmark discovery was somewhat of a let-down, the scientists said.

The team used images from the Hubble space telescope to identify 43 possible faraway galaxies and then used state-of-the-art spectrographic equipment at an observatory in Hawaii to confirm their distances. In the end, Finkelstein and his colleagues could retrieve data from only this lone galaxy.

"We were first excited, then a little disappointed because we only saw one, and then excited again," he said. "We would have hoped for some number bigger than one."

With advances in instrumentation technology, astronomers continue to stretch their detection capabilities further outward from the Milky Way. Because light takes time to travel such long distances, remote objects allow them to peer back through time.

The light detected from this outlying galaxy - with the official catalogue name z8-GND-5296 - left the galaxy 13.1 billion years ago. This gives us a glimpse of the universe as it was when it was only 700 million years old.

In other words, we are looking 95 per cent of the way back to the big bang.

Setting out to find the most distant galaxy isn't a single moment, but rather a careful process of confirmation and remeasurement. Further away galaxies than z8-GND-5296 have been identified but failed a double-check process.

The team first studied a month's collection of images from the Hubble telescope for possible candidate galaxies. Hubble avoids the problems that earthbound telescopes can face, such as cloud and bad weather, to more easily spot the red blobs that signal a distant object.

The same effect that causes a passing ambulance siren to change pitch as it zooms by, called the Doppler shift, makes the most distant galaxies appear red. Because the universe is expanding, the galaxy's light moves away from us and gets stretched into a redder wavelength.

This article appeared in the South China Morning Post print edition as Galaxy is the most distant yet found